The present invention relates to manufacturing welded wire reinforced concrete pipe, specifically to spacing the welded wire reinforcement assembly from the pipe form during the operation wherein concrete is formed around the wire reinforcement.
A wire reinforcing assembly typically comprises at least a generally cylindrical wire reinforcing cage. Sometimes, it includes inner and outer cages. This cage usually has a plurality of longitudinal wires running lengthwise thereof and a plurality of generally circumferential wires joined to the longitudinal wires and being generally parallel to one another. Sometimes, additional reinforcement in the form of stirruping or quadrant reinforcing is added to the cage assembly.
Once the cage assembly is completed, it is placed in a pipe form. A single external wall form is used when the pipe is formed in a packer head machine and a double wall form is utilized when concrete is to be cast around the cage.
Spacers have to be secured to the cage assembly in order to space it from at least one of the form walls. Typically, a short steel rod is welded or otherwise secured to the reinforcing cage to serve as a spacer. A plurality of such rods are secured to the cage at spaced points along the length and around the circumference of the cage. Plastic spacers are also available which snap onto the cage at various points.
In the case of either type of spacer, it is very time-consuming to secure the spacers to the pipe reinforcing cage. Yet, this is an important operation in that if the wire reinforcing cage gets too close to a form wall, it will protrude through the concrete at the surface of the concrete pipe wall. Such protrusion results in rejection of the pipe since it would not conform to engineering standards.